Spring Break means car fix time!

[Manarius]

Problem at hand: When the car is cold, it hesitates a lot. I press on the gas and the car does not go smoothly (it also sounds bad). I posted a youtube video of it a while ago, but I'll link to it again: http://youtube.com/watch?v=9Efjxpy4DYc

First thing I did when I got on break was replace the coolant temperature sensor. Then, after that I checked the ECU codes and the computer threw 3 codes. The first code was the CTS sensor (obviously). However, the other two have me stumped.

The first code was code 31, for the Throttle Position Sensor. I made a thread about this earlier and I adjusted it to proper spec (.5v). Maybe this code is from previously? I'm pretty sure I cleared the codes after I replaced the sensor. Assuming I did, why would it come back? This sensor was brand new when I put it in.

The second code was 56, for the EGR system. What does this mean? I tried searching for EGR, nothing came up . What exactly does this system do and would it cause the problems noted?

One of the comments on the youtube video was that an O2 sensor could cause this problem as well, however the ECU isn't throwing a code for it. Is that a reasonable guess?

I have a week to work on this stuff so that's why I'm starting now. I can afford most cheap fixes.

[Manarius]

Nobody?

[Crazy_pilot]

I think I might have the same hesitation. It feels like the car just doesn't want to get moving, right? Like around 1700-2200 RPM there's no power and it just won't accelerate unless you step on it a bit. I replaced my TPS, which didn't solve the problem. A little while ago I replaced the alternator, and the mechanic at work unplugged the signal wire clip from the alternator while the car was running. When I left work that day, it was like a new car. Absolutely no hesitation, perfect acceleration, etc. That lasted about a day.

If there's anyone who has an idea I'd also be interested. It's very annoying, and when I let my very attractive friend drive the car because she wants some practise for her driving test, I don't like her saying my car drives like crap.

Edit: I'm not throwing a code for the TPS, but I have gotten intermittent codes for both O2's, which may be caused by leaking oil dripping onto the sensors and plugging the backside.

[JaySVX]

If it says EGR you might want to check the egr valve, as well as the vacuum lines to see that there aren't any disconnected or broken. EGR, from my limited knowledge, allows for the recycling of exhaust fuel, to get a more complete burn. Example:

Each time the cylinder approaches Top Dead Center, it does this:

Cycle 1: Combustion
Cycle 2: Exhaust
Cycle 3: Exhaust back in, ignited a second time to burn remaining fuel vapors
Cycle 4: Final exhaust

Thus, the 4 cycle engine!

Apparently, the EGR valve allows for the 3rd cycle to complete properly. The EGR is vacuum controlled, and has a little plunger thing in it, that you can push in and pull out. If there's a vacuum leak, it won't function properly. If the egr valve gasket is bad, it won't function properly. It won't/shouldn't hurt acceleration or fuel economy on a noticeable level, just makes your exhaust dirtier. Hope this guides you in the right direction.

Please note, the above is pure speculation based entirely on limited knowledge and logic to connect point a to point b. Hopefully someone with more knowledge can chime in on this one.

[Crazy_pilot]

Originally Posted by JaySVX

Each time the cylinder approaches Top Dead Center, it does this:

Cycle 1: Combustion
Cycle 2: Exhaust
Cycle 3: Exhaust back in, ignited a second time to burn remaining fuel vapors
Cycle 4: Final exhaust

Thus, the 4 cycle engine!

Ummm...hate to burst your bubble, but the 4 cycles of an engine are intake, compression, combustion, exhaust.

You were right-ish about the EGR's function though, it allows a certain amount of exhaust gas back into the intake. Exhaust gases, specifically NO2, are fairly inert and won't combust like oxygen. The main purpose of the EGR system is to lower emmisions levels. It actually kills engine performance a bit, because you're drawing in something that the engine can't burn.

[TomsSVX]

Originally Posted by Crazy_pilot

Ummm...hate to burst your bubble, but the 4 cycles of an engine are intake, compression, combustion, exhaust.

You were right-ish about the EGR's function though, it allows a certain amount of exhaust gas back into the intake. Exhaust gases, specifically NO2, are fairly inert and won't combust like oxygen. The main purpose of the EGR system is to lower emmisions levels. It actually kills engine performance a bit, because you're drawing in something that the engine can't burn.

He's right

The emmisions level for NOX is reduced by the EGR, which is why if your EGR is malfunctioning, it will usually fail for NOX emmissions

Tom